Electrophotographic processes for producing a permanent image on media are well known and commonly used. In general, these processes all include devices for: (1) charging a photoreceptor which is a drum or continuous belt bearing a photoconductive material; (2) producing an electrostatic latent image by exposing the charged area to a light image or a light emitting diode array, or scanning the charged area with a laser beam; (3) presenting particles of toner to the photoreceptor surface upon which the electrostatic latent image has been formed so that the particles are transferred to the electrostatic latent image; (4) transferring the particles from the photoreceptor to the media while maintaining the shape of the image formed on the photoreceptor drum; (5) fusing or fixing the particles in the shape of the image to the media; and (6) cleaning or restoring the photoreceptor for the next printing cycle.
Referring to FIG.1, the electrophotographic printer 300 of the prior art has therein feed rollers 321 and 322 for feeding the printing sheets stacked in the printing sheet cassettes 311 and 312, a pair of rollers 323 for conveying a printing sheet fed from the printing sheet cassettes 311 or 312, an exposure array 376 for emitting light to the photosensitive drum 52 for forming an electrostatic latent image on the photosensitive drum 52, a transfer electrostatic charger 327 for transferring toner from the photoconductive drum 52 to the printing sheet, a pair of heat rollers 328 for fixing the toner transferred on the printing sheet and a prior art electrophotographic cartridge 50.
The electrophotographic cartridge 50 has an electrostatic charger 84 for electrostatically charging the photoconductive drum 52 uniformly, a developer assembly 54 for applying toner to the electrostatic latent image formed on the photoconductive drum 52 after exposure to the exposure device 376, and a cleaner 76 for removing the untransferred toner which remains on the photoconductive drum 52 after the transfer step. The untransferred toner is stored in waste hopper 85. Electrostatic charger 84 may be a charge roller assembly or a corona assembly. Further information about alternative photographic processes is available in the text "The Physics and Technology of Xerographic Processes", by Edgar M. Williams, 1984, a Wiley-Interscience Publication of John Wiley & Sons, the disclosure of which is hereby incorporated by reference.
Many image forming apparatus utilize the electrophotographic printing process, examples being laser printers, copy machines, and facsimile machines. As described above, these image forming apparatus use toner to print or copy the desired image or words onto a piece of paper or media. The toner is contained in a reservoir which is depleted as a result of printing. For example, the toner in a laser printer is generally depleted after printing from 2,000 to 30,000 pages depending upon the initial supply of toner in the reservoir and the coverage of the text or graphics images printed.
Monochrome Electrophotographic printers are typically designed so that the components involved in actually accomplishing electrophotographic printing are contained in a disposable electrophotographic print cartridge. The disposable toner cartridge, is conventionally identified as a "consumable" or "consumable product" because of its limited "life" (i.e., the toner will eventually deplete or some other component will eventually wear out). The components usually included in the disposable cartridge are the photoconductor drum, the drum charging assembly, such as the charge roller assembly or the corona assembly, the developer assembly, the drum cleaning blade, and the supply of toner used for forming the print text or print images. These items and other similar components are also commonly identified as consumables because they too have a limited life. The supply of toner is contained in a toner reservoir. The useable life of the cartridge is limited by the available supply of toner in the toner reservoir and the useable life of the cartridge components, particularly the photoconductor, the developer assembly, and the drum charging assembly. Upon exhaustion of the toner supply in the cartridge, it is necessary to replace the empty cartridge with one having the reservoir filled with toner.
Color Electrophotographic printers generally do not have a single toner cartridge. However, the consumables still need to be replaced as they are depleted. Some color electrophotographic printers allow the user to replace each individual color of toner independent of changing the photoconductor drum or belt.
New consumables installed in electrophotographic printing devices often must print several pages (up to 25 pages) to "condition" the consumable before use. This "conditioning" is required to allow various components to reach optimal condition for printing. Functions such as the distribution of lubrication from the cleaning blade on the photoconductor, pre-stirring of the toner, conditioning of the developer sleeve, etc. are performed during this "conditioning" time.
This approach is especially troublesome for printer users who have had a printing job interrupted due to a consumable issue, such as running out of toner. Prior to the present invention, if a printing job is interrupted due to a consumable issue, installation of the new consumable will result in the immediate continuation of the printing job. The first several pages (up to 20) may have print quality defects and thus affect the entire print job adversely. As an example, a customer may be printing an instruction manual which is several hundred pages in length. During the printing one of the consumables is exhausted stopping the printing process. The user installs a new consumable the printer begins printing again. If a "conditioning" problem exists, up to 20 pages could have print quality defects. These pages would be in the middle of the printed material and would degrade the print quality of the entire job. Most manufacturers do not provide warranty coverage of consumables from page 1, but rather specify a few pages of unwarranted printing at the beginning of consumable life.